1. Field of the Invention
The present invention relates to a volumetric 3D display panel and a volumetric 3D display system using the volumetric 3D display panel. More particularly, the present invention relates to a volumetric 3D display panel formed by stacking a plurality of transparent, flexible display panels like organic light-emitting devices to have a curved surface and a volumetric 3D display system using the volumetric 3D display panel.
2. Description of the Related Art
A three-dimensional (3D) image is formed according to the principle of stereoscopic vision through two eyes of a human being. A binocular parallax, which is generated due to the separation of the two eyes by about 65 mm, can be considered as the most important factor of a cubic effect. In various fields, such as, medical images, games, advertising, education, military affairs, 3D image display based on the binocular parallax principle is recently in great demand. Moreover, with the gradual popularization of high-resolution TVs, popularization of 3D TVs through which viewers can view 3D images is anticipated in the future. Hence, various stereoscopic display techniques have been proposed.
General stereoscopic display techniques are roughly classified into a glasses stereoscopic display technique, a glass-less stereoscopic display technique, and a perfect stereoscopic 3D display technique.
In both a glasses stereoscopic display technique and a glass-less stereoscopic display technique, two 2-dimensional images having parallax therebetween are provided to the left eye and the right eye, respectively, of a human to provide a stereoscopic effect. However, the glasses stereoscopic display technique requires a viewer to wear a special accessory, such as, polarized glasses, to enjoy a 3D image. In the glass-less stereoscopic display technique, only a viewer positioned at a predetermined location can view a 3D image, because there is only one viewing zone or there are several separated viewing zones. Furthermore, both the glasses and glass-less stereoscopic display techniques have a limit in that only a depth of an object is reproduced, that is, viewers cannot enjoy all of images of an object as viewed in various directions.
To solve these problems, the perfect stereoscopic 3D display technique has been proposed, in which a convergence angle made by the left and right eyes viewing an image is consistent with a focal point of the two eyes so that a perfect 3D image can be recognized. Examples of the perfect stereoscopic 3D display technique include integral photography and holography. However, integral photography has a disadvantage in that a parallax range and a viewing angle obtained by a lens are restricted. Holography has disadvantages in that a coherent light source, such as, a laser, is required and that recording and reproducing a large object located at a far distance is difficult.
A volumetric 3D display technique also belongs to a perfect stereoscopic 3D display technique. FIG. 1 schematically illustrates a conventional volumetric 3D display device employing a volumetric 3D display technique. Referring to FIG. 1, the conventional volumetric 3D display device includes a projector 10 for projecting an image and a multi-plate optical panel 11 onto which the image from the projector 10 is projected. The multi-plate optical panel 11 is a stack of a plurality of optical plates 11a through 11e. Each of the optical plates 11a through 11e is, for example, a controllable, variable, semitransparent liquid crystal device. When turned off, the optical plates 11a through 11e become transparent so that the image from the projector 10 can pass through the optical plates 11a through 11e. When turned on, the optical plates 11a through 11e enter into an opaque light-scattering state so that the image from the projector 10 can pass through the optical plates 11a through 11e. 
In this structure, the projector 10 produces a 3D image on the multi-plate optical panel 11 by consecutively projecting a plurality of images having different depths onto the optical plates 11a through 11e using a time-division technique. More specifically, the protector 10 sequentially projects first through fifth images Im1 through Im5 onto the optical plates 11a through 11e according to a time-division technique. Each of the optical plates 11a through 11e enters into an opaque light-scattering state when a corresponding image is projected from the projector 10. Then, the first through fifth images Im1 through Im5 are sequentially projected onto the optical plates 11a through 11e, respectively. Since the projection of the plurality of images is accomplished within a very short period of time, an observer perceives the plurality of images to be a single 3D image Im6. Hence, a visual effect where a 3D object seems to be formed within a space is obtained.
However, the projector 10 should raster at ultrahigh speed to produce a natural 3D image from a plurality of 2D images. To display a 3D image without flickering, the projector 10 should project the plurality of 2D images onto the optical plates 11a through 11e at a speed of at least 1.5 Khz to 2 Khz. Hence, the conventional volumetric 3D display device requires a projector capable of projecting an image at a speed of several thousands of Hz.
FIG. 2 schematically illustrates another conventional volumetric 3D display device. In the conventional volumetric 3D display device of FIG. 2, a projector 20 consecutively projects images onto a bent screen 22 installed within a cylindrical frame 21 and simultaneously rotates the screen 22 at high speed, thereby obtaining a 3D image. However, in the conventional volumetric 3D display device, a motor (not shown) for rotating the screen 22 may generate noise, and forming a large volumetric 3D display system using a large screen is difficult due to friction between the screen 22 and the frame 21 and air resistance. Furthermore, a volumetric 3D display system using the conventional volumetric 3D display device is prone to break due to the friction and air resistance, so that the lifespan of the system decreases.